Angular transducer unit and method for its manufacture, as well as angular switching device and device for the detection of objects

ABSTRACT

The present invention relates to a method for the manufacture of a transducer unit for an angular switching device, in which a transducer element is inserted and fixed in an angled bush. The inventive method is characterized in that the transducer element is brought into aligned engagement with a transducer receptacle formed in a tool, that subsequently for the precise positioning with respect to the transducer element the bush is brought into an aligned, at least partial positive engagement with a bush receptacle appropriately constructed in the tool and that for completing the transducer unit the transducer element is fixed in the bush. In further aspects the invention relates to an angular transducer unit, an angular switching device and an object detection device.

In a first aspect the present invention relates to a method for themanufacture of a transducer unit for an angular switching device. Infurther aspects the invention relates to a transducer unit manufacturedthrough the method, to an angular switching device and to a device forthe detection of objects.

Angular switching devices, i.e. switching devices in which a detectionor radiation area of a transducer assumes an angle of e.g. 90° relativeto the casing axis of the switching device are e.g. known from DE 201 06871 U1. Such an angular switching device has the following components:an angular transducer unit with a transducer element, a casing sleevefor receiving electronics, in which the transducer unit is positioned atone end of the casing sleeve, and a connection part positioned at asecond end of the casing sleeve for connection to external equipment.

Such angular switching devices are appropriately then used whereconventional switching devices with a substantially axially extendingdetection or radiation area are unusable for space reasons, i.e. where avery compact layout of the switching devices is necessary or desired.

A device according to the preamble for the detection of objects,particularly for the detection of labels, is described in EP 1 067 053A1. In that case transmitters and receivers are housed in a forkedcasing.

Angular switching devices are also described in EP 1 067 053 A1, DE 20005 283 U1, DE 100 58 480 A1 and DE 30 08 309 C2.

DE 43 28 366 C3 and DE 195 21 361 A1 relate to axial switching devices.

A device for the detection of multiple sheets is disclosed in U.S. Pat.No. 4,066,969.

In the manufacture of an angular transducer unit a transducer element isinserted and fixed in an angled bush. The term angled bush is hereunderstood to mean a tubular component with a first, axial opening forconnection to a casing sleeve of a switching device and with a secondopening transversely to the axial direction. The second opening is theentrance or exit opening for the transducer element.

Compared with axial switching devices the relative positioning of thetransducer element relative to the bush is more difficult in the case ofan angular transducer unit, because there the positioning cannotessentially be obtained by centring with respect to the casing axis.

The object of the present invention is to provide a method for themanufacture of an angular transducer unit for an angular switchingdevice with which such transducer units can be very preciselymanufactured, that can be easily and inexpensively performed and is alsosuitable for an industrial scale production. In addition, an angulartransducer unit, an angular switching device and an object detectiondevice are to be provided, which are also easy and precise tomanufacture.

In a first aspect this object is achieved by the method having thefeatures of claim 1.

Advantageous variants of the method and preferred embodiments of theinventive angular transducer unit, angular switching device and objectdetection device form the subject matter of the subclaims.

The method of the aforementioned type is inventively further developedin that the transducer element is brought into aligned engagement with atransducer receptacle formed in a tool, that subsequently the bush forprecise positioning with respect to the transducer element is broughtinto an aligned and at least partly positive engagement with a bushreceptacle suitably formed in the tool and that for the production ofthe transducer unit the transducer element is fixed in the bush.

In the case of the angular transducer unit according to the inventionprior to the fixing of the transducer element it can be received withclearance in the bush and the transducer element is given a definedpositioning with respect to the bush with the aid of a tool,particularly in accordance with the inventive method.

In the case of the angular switching device according to the inventionthe angular transducer unit is manufactured in accordance with theinventive method.

A first fundamental principle of the invention is that the assembly ofthe transducer element and bush requires the use of a suitably shapedtool, which can also be referred to as a stop fitting or form. In saidtool is formed a transducer receptacle with which the transducer elementis inventively brought in a first method step into aligned engagement.

A further fundamental principle of the invention is that for the precisepositioning of the bush relative to the transducer element the bush isalso brought into an aligned engagement with the tool. For this purposethe tool is also provided with a suitably shaped bush receptacle.

A first major advantage of the inventive method is that the precisionand reproducibility of positioning can be significantly improved. Thus,the inventive method is particularly suitable for industrial scaleproduction.

A second important advantage is that the method can be performed usingsimple means, i.e. inexpensively.

With the method according to the invention, if the transducer elementhas a clearance in the angled bush, i.e. is not positively receivedthere, the relative position of bush and transducer element can beadjusted precisely and in a defined manner by a suitable choice of tool.Thus, there is a high manufacturing variability.

It is also advantageous that in the case of a possibly modified relativeposition between transducer element and bush, it is not necessary toreplace the shaping tools for the transducer element and/or bush, butinstead only the much less expensive positioning tool.

In a preferred variant of the inventive method the transducer element isfixed relative to the tool. This facilitates the relative positioning ofthe transducer element with respect to the bush and safety is increased.

The transducer element can e.g. be fixed by vacuum, adhesives,particularly an adhesive tape, and/or by magnets.

If e.g. using the same tool body it is wished to manufacture transducerunits using transducer elements of different sizes, it can beappropriate for the transducer receptacle to at least partly be formedby a transducer centring device, which is inserted or engaged in a toolbody of the tool.

In a particularly preferred variant of the method a transducer elementis initially appropriately aligned relative to the tool body using atransducer centring device, and fixed e.g. by a vacuum. The transducercentring device is then removed again, so that after filling the gapswith foam or moulding material, by means of the hardened foam orhardened moulding material, the transducer surface and a bush boundarysurface form a planar termination.

If transducer units with bushes of different size are to be manufacturedwith the same tool body, it can be appropriate for the bush receptacleto at least partly be formed by a bush centring device, which isinserted or engaged in the tool body.

Additional safety can be obtained through the transducer centring deviceand/or bush centring device being fixed with respect to the tool body.

In principle, any type of fixing can be used. For example, thetransducer centring device and/or bush centring device can be fixed byadhesives, particularly an adhesive tape, and/or by vacuum. However, avariant of the method in which the transducer centring device and/orbush centring device is fixed by magnets is particularly easy toperform.

It can also be appropriate in this connection to fix the bush relativeto the tool, particularly using a holder provided on the tool.

If the transducer element is to be fixed by vacuum with respect to thetool body, the transducer element can be sucked onto the tool by meansof at least one vacuum duct in the tool body.

In a particularly simple manner the transducer element can be connectedor fixed relative to the bush if gaps in the bush are at least partlyfilled with foam or moulding material. Known materials can be used forthis purpose.

An outward passage of foam or moulding material as a result of a suctioneffect of the vacuum and resulting problems in the case of a relativealignment can be avoided if a pressure compensation takes place onradially outer areas of a sucked on transducer element usingcompensating ducts in the tool body.

In a particularly preferred variant of the method use is made of a toolwith steps, which as a stop can engage with a front end and/or a setbackshoulder of the bush. The steps make it possible in simple manner tobring about an at least partial positive engagement of the bush with thetool.

In connection with large scale production it is also advantageous tomanufacture several transducer units in parallel using a single toolwith a plurality of transducer receptacles and bush receptacles. Thestep-like tool body variant is e.g. particularly appropriate forconstruction using a plurality of transducer and bush receptacles.

To avoid the influence of interfering radiation on the transducerelement in operation, the inside of the bush can be at least partlymetallized or use can be made of a shielding can pressed into the bushby positive engagement.

A particularly stable structure and a clearly defined alignment of thecomponents is brought about by fixing, particularly soldering theshielding can to a printed circuit board.

It is also appropriate in this connection to solder the transducerelement to the shielding can, particularly by means of a clip providedthereon.

Additionally or alternatively the bush can be brought into a positiveand/or non-positive engagement, particularly a locking engagement with aprinted circuit board.

The functionality of the transducer units can be increased by insertingand fixing several transducer elements in an angled bush.

The transducer unit according to the invention can in principle be usedboth as a transmitter and a receiver. The transducer element can e.g.have a random sensor, particularly an inductive, optical, capacitive,temperature, pressure and/or ultra-sonic sensor.

It is particularly useful to use an inventive transducer unit in aswitching device constructed as a proximity switch and which operatescyclically and/or in a barrier operation.

A cyclic switching device is here understood to mean a device in which atransducer emits a signal and simultaneously or optionally with a timelag the response from a possibly present object is detected. As opposedto this in the case of a barrier, e.g. a count barrier, a separatetransmitter and separate receiver are provided.

Undesired irradiation of the inventive switching device can be reducedor avoided if a shielding sleeve is provided for shielding purposes inthe casing sleeve of the switching device.

Such a switching device is preferably manufactured in a single-operationmethod, such as is e.g. described in German patent application 103 59885.5.

Alignment of the switching device is made easier if the casing sleeve isangular and in particular square in profile. However, a cylindricalcasing sleeve permits a variable or a standardized switching devicepositioning in proximity switch technology.

The inventive switching device permits a very high functionality. Inparticular, the switching device can be constructed as a transmitterand/or receiver. There can also be several transducer elements,optionally also in several bushes.

The advantages of the inventive switching device can be particularlyappropriately used in a device for the detection of objects with atleast one transmitter for emitting a measuring signal in a detectionarea and with at least one receiver for receiving an incoming signalfrom the detection area, the transmitter and/or receiver beingconstructed as an inventive, angular switching device. Both thetransmitter and receiver can be in an angular, more particularlyprofile-square/cylindrical casing shape.

When a very compact installation is required, it is advantageous toprovide an evaluating unit, where the transmitter, receiver andevaluating unit are in each case housed in separate casings. Thus,receiver and transmitter are offset from the evaluating unit.

In a further advantageous and particularly inexpensive solution of theinventive device the transducer elements are directly fitted in aseparate, very short bush (approx. 8 to 12 mm), which can also be calleda transducer receptacle, this taking place orthogonally to the circuitboard plane. To cut down costs, the transducer unit is treated like anelectromechanical component, which is solderable to the circuit board bymeans of at least one clip on the bush-like shielding can. A mechanicalalignment, particularly with respect to the parallel positioning, takesplace by means of the transducer receptacle resting flat on the circuitboard. To avoid an inadmissible stressing of the soldered joints inspecial cases the transducer receptacle can have pins and/or detents,which engage in the circuit board, mechanically fix the same and at thesame time form a stop with respect to said circuit board. Additionalstrength can be brought about by an adhesive fixing of the transducerreceptacle and/or the bush-like shielding can. If a metallic shieldingcan is unnecessary or is unusable, alternatively use can be made of abush-like can which has a locking engagement with the printed circuitboard.

Such a device is particularly suitable for detecting or recognizingsingle, missing and/or multiple sheets, e.g. in printing presses. Forthis purpose the transmitter is appropriately an ultrasonic and/oroptical transmitter and/or a capacitive sensor is provided, the receiverthen being constructed with corresponding ultrasonic and/or opticalsensors, or in the case of a capacitive sensor a precisely alignedcapacitor element must be formed.

The supply of transmitter and receiver can also take place separately,so that there is no need for a connection between the transmitter unitand receiver unit. This can in particular be necessary if significantdistances are to be bridged with angled barrier layouts or very wideobjects are to be measured, particularly paper webs.

As a result of the angular design of the switching devices, the devicecan be constructed in a particularly compact manner opening up new areasof use.

A defined relative positioning can be achieved in a particularly simplemanner if the transmitter and receiver are located in a joint holder.

As the electronics for the transmitter normally take up less space thanthe electronics for the receiver, in an inexpensive variant thetransmitter can be constructed as an axial switching device.

Further advantages and features of the method according to theinvention, the angular transducer unit, the angular switching device andthe device for the detection of objects are described in greater detailhereinafter relative to the attached diagrammatic drawings, whereinshow:

FIG. 1 A plan view of a tool for performing the inventive method.

FIG. 2 The tool of FIG. 1 in a view from the front.

FIG. 3 The tool of FIG. 1 in a sectional view along lines 3-3.

FIG. 4 A plan view of a bush centring device for insertion in the toolof FIG. 1.

FIG. 5 The bush centring device of FIG. 4 in a sectional view alonglines 5-5.

FIG. 6 The bush centring device of FIG. 4 in a sectional view alonglines 6-6.

FIG. 7 A sectional view of the tool of FIG. 1 in accordance with FIG. 3with inserted bush centring device.

FIG. 8 A sectional view corresponding to FIG. 7 with inserted transducerelement and a bush brought into the stop position.

FIG. 9 A part sectional view of a transducer element vacuum-fixed to thetool and with a bush in a first embodiment.

FIG. 10 In a part sectional view a transducer element vacuum-fixed tothe tool and with a bush in a second embodiment.

FIGS. 11 to 13 Examples for the use of the inventive angular switchingdevices in object detection devices.

FIG. 14 A perspective view of an embodiment of an inventive device forthe detection of objects, particularly single, missing or multiplesheets.

FIG. 15 A plan view of the device of FIG. 14.

The method according to the invention for the manufacture of an angulartransducer unit 12 will now be described relative to FIGS. 1 to 8. Atool 40 used in this connection is shown in different representations inFIGS. 1 to 3. This tool 40 essentially comprises a tool body 42, whichcan e.g. be made from steel. In said tool body 42 is formed a bushreceptacle 46, which in the example shown has a substantially squarebase surface with rounded corners. Within said bush receptacle 46 isformed a transducer receptacle 44 as a circular disk-shaped depression.In the manner shown in FIG. 2, for fixing a bush in the bush receptacle46 a holder 48 is provided, which is held on the tool body 42 with theaid of magnets 52. As can be seen in FIG. 3, the tool body 42 isprovided in the vicinity of bush receptacle 46 with a stepped,staircase-like profile with two steps 50 which, as shown e.g. in FIG. 8,can be brought into aligned engagement with a bush 16.

FIGS. 4 to 6 show a U-shaped bush centring device 54 to be inserted orengaged in the bush receptacle 46 of the tool body 42. Bush centringdevice 54 can also be made from steel. In FIG. 7 is shown across-sectional view of the tool 40 with inserted bush centring device54.

FIG. 8 provides a corresponding sectional view of a bush 16 brought intostop engagement with tool 40. A transducer element 13 is fixed inaligned manner in transducer receptacle 44 using an adhesive film 56.The transducer receptacle 44 is constructed as a roughly 0.1 mm deepdepression for receiving adhesive film 56. A bush centring device 54 isinserted in the tool body 42 and forms the bush receptacle 46 for bush16. As can be gathered from FIG. 8, a front end 19 of bush 16 engageswith an inside of the bush centring device 54 and a setback shoulder 18of bush 16 with a step 50 of tool body 42. This provides a precisealigned positioning of bush 16 relative to tool 40. Stop engagement ofthe setback shoulder 18 with step 50 does not take place if saidshoulder 18, due to the manufacture of the bush 16, is not preciselydefined. Finally bush 16 is fixed with the holder 48 with respect to thetool 40, so that in the situation shown in FIG. 8 manufacture of thetransducer unit 12 can be completed by connecting transducer element 13to bush 16, e.g. by foam filling of the gaps.

Method variants in which the transducer element 13 is fixed by vacuumwith respect to the tool body 42 will be explained with reference toFIGS. 9 and 10. In a part sectional view FIG. 9 shows a situation inwhich a transducer element 13 and a bush 16 are inserted on or in a toolbody 42. A precise alignment of the bush 16 can take place in the mannerdescribed above relative to FIG. 8. The transducer element 13 is suckedagainst the tool body 42 by means of a vacuum produced in a vacuum duct60. A seal 58 is inserted in a circumferential groove in tool body 42and ensures adequate vacuum sealing. The seal 58, which can e.g. be anO-ring, is consequently used for sealing the transducer surface.

If the transducer element 13 is correctly positioned relative to bush16, for fixing transducer element 13 relative to bush 16 the gaps 21 arefilled with foam 17. For this purpose a foam nozzle is inserted in bush16 through a rear opening 23 in the latter (see FIG. 8). Therefore bush16 is made as short as possible. To prevent a foam overflow over surface26 defined by transducer element 13 and bush 16, the transition areabetween transducer element 13 and tool body 42 is additionally sealed.For this purpose, in the variant shown in FIG. 9, a further seal 59 isprovided and is also inserted in a circumferential groove in tool body42. Whereas seal 58 brings about vacuum sealing, seal 59, which can e.g.be an O-ring made from very flexible silicone, ensures an adequate foamor residual pressure seal to avoid a suction effect on the liquidfilling material, particularly the foam. Thus, said seal 59 ispositioned as far as possible radially to the outside relative totransducer element 13. Seals 58 and 59 must be carefully matched to oneanother, so that seal 59 is always pressed down and consequently ensuresboth an adequate vacuum sealing and foam sealing. In practice, seal 59is made from a more flexible material than seal 58.

In the embodiment illustrated in FIG. 10 the area between transducerelement 13 and tool body 42 is sealed by a rubber base 61 in order toobtain a suitable foam sealing.

An underfoaming of the transducer element 13 is also avoided in theexamples disclosed by a pressure compensation taking place incompensating ducts 62 radially surrounding the vacuum ducts 60. Thus,there is no pressure gradient between the gaps 21 to be foamed and thepressure compensating ducts 62, so that under vacuum pressure action ona transducer ceramic there is no suction pressure on the foam. Animportant advantage can be achieved as a result of this in that thehardened foam, the transducer surface and the boundary surface of thebush 16 form a planar, well-defined termination. The quality of thisplane is then essentially limited by the manufacture of the transducersurface and/or the bush surface. Any foam residues can optionally beremoved by a cutting mould.

A precise alignment of transducer element 13 can be brought about withthe aid of a centring form not shown in FIGS. 9 and 10 and which canalso be referred to as a transducer centring device. Such a centringdevice can be placed in or on tool body 42 and a transducer element 13can then be brought into aligned engagement therewith, i.e. in thesimplest case inserted therein. Before or after this the vacuum can beconnected in, so that the transducer element 13 is sucked onto the toolbody 42. The centring device can then be removed, so that followingfoaming the transducer surface, boundary surface of the bush andhardened foam can form a planar termination.

For removing the centring device or centring mechanism the tool body 42can be provided with a suitable guide, which in particular ensures theparallel nature of the removal.

Thus, the method brings about a clean, well defined boundary surface ofthe transducer element 13, which can e.g. be a piezoelectric element,the boundary surface of bush 16 and the hardened foam. A simple centringof the piezoelectric ceramic by hand or machine can, as described, takeplace by a centring form, which can also be called a transducer centringdevice. Said device, e.g. following the suction action of the transducerelement 13 or following an adhesion of said element 13 with an adhesivefilm, can be easily removed. The bush 16 can then be pressed on bymachine, particularly using a siphon and can be aligned with respect tothe bush receptacle 46 in tool 40. This permits automated production,i.e. large scale industrial production.

Numerous variants of the object detection devices 70 according to theinvention are shown in FIGS. 11 to 15. With each of said devices 70there is a transmitter 72 for emitting a measuring signal in a detectionarea 79 and a receiver for receiving an incoming signal from detectionarea 79. In the variants shown the transmitter 72 is positioned facingreceiver 74 in such a way that the radiation area of transmitter 72 andthe receiving area of receiver 74 are substantially symmetrical to acommon axis 78. As a function of the interaction of the objects to bedetected with the irradiated radiation, in principle other arrangementsare also possible.

In the case of the embodiments of FIGS. 11 to 13 transmission through anobject located in detection area 79 or the shielding of the radiationthrough said object is measured. If in an alternative development thereflection through an object to be detected is to be measured,transmitter and receiver are arranged with a geometry determined by thereflection law.

In the three variants shown in each case the transmitter 72 is connectedby a connecting line 73 to receiver 74, which is in turn connected by aline 75 to the corresponding supply and evaluating units.

In the embodiment of FIG. 11 transmitter 72 is axially constructed,which is particularly inexpensive.

A particularly compact example of a device for the detection of objects70 is shown in FIG. 12, where both the transmitter 72 and receiver 74 isconstructed as an angular switching device according to the invention.

A variant of the example of FIG. 12 is shown in FIG. 13, wheretransmitter 72 and receiver 74 are located in a joint holder 76, whichpermits a precise relative orientation of transmitter 72 and receiver 74in a simple manner. This example is shown in greater detail in FIGS. 14and 15, the corresponding components always having the same referencenumerals.

FIG. 15 shows the basic structure of the inventive angular switchingdevices 10. An inventively manufactured transducer unit 12 is insertedat a front end 22 in a casing sleeve 14. At a rear end 20 of casingsleeve 14 is provided a connection part 24 or 25 by means of whichelectronics in the casing sleeve are connected to external supply andevaluating devices. Said switching devices 10 can be advantageouslymanufactured by a single-operation method, such as is e.g. described inGerman patent application 103 59 885.5. For this purpose a transducerunit 12, a support with an electronic circuit, a shielding sleeve andthe connection part 24, 25 form a module, which is then inserted intothe casing sleeve 14 from front end 22. There is no need for separatecentring measures.

Connection parts 24, 25 are preferably made in a fully transparentmanner, so that via suitable lighting means a status display to theoutside can take place. The transparent construction permits aquasi-all-round visibility, such as is e.g. described in German patentapplication 103 43 529.8.

The variants of the devices for the detection of objects 70 shown inFIGS. 11 to 15 can e.g. be constructed as ultrasonic barriers withultrasonic transmitters 72 and ultrasonic receivers 74. Such ultrasonicbarriers and sensors are more particularly used in paper-processingmachines, such as scanners, copiers and paper cutting machines. Ingeneral, for the detection of the corresponding paper sheets, i.e.particularly for detecting single, multiple and/or missing sheets, highfrequency sound is used.

In alternative variants use can be made of light sensors or acapacitance measurement is performed. The sensors arranged in angularmanner permit a very good installation solution, particularly withmachines where the space conditions are very confined, especially in thecase of a small construction hight. Although it is still very compact,the variant of FIG. 11 is very inexpensive, the transmitter 72 beinghoused in an approximately 20 mm long casing sleeve.

1. Method for the manufacture of an angular transducer unit for anangular switching device, comprising: inserting and fixing a transducerelement in an angled bush, wherein the angled bush comprises a tubularcomponent having an axial direction and an opening opening transverselyto the axial direction for receiving the transducer element, theinserting and fixing of the transducer element in the angled bushcomprising: bringing the transducer element into aligned engagement witha transducer receptacle in a tool, inserting or engaging a bush centringdevice in a body of the tool to form a bush receptacle, bringing thebush into an aligned, at least partial engagement with the bushreceptacle in the tool, to position the bush with respect to thetransducer element, fixing the transducer element in the bush, and atleast partially forming the transducer receptacle by inserting orengaging a transducer centring device in the tool body.
 2. Methodaccording to claim 1, further comprising fixing the transducer elementrelative to the tool.
 3. Method according to claim 2, wherein the fixingof the transducer element is provided using at least one of: vacuum,adhesives, adhesive tapes, or magnets.
 4. Method according to claim 1,further comprising fixing the transducer centring device relative to thetool body.
 5. Method according to claim 1, further comprising fixing thebush centring device relative to the tool body.
 6. Method according toclaim 4, wherein the fixing of the transducer centring device isprovided using at least one of: adhesives, adhesive tapes, vacuum, ormagnets.
 7. Method according to claim 5, wherein the fixing of the bushcentring device is provided using at least one of: adhesives, adhesivetapes, vacuum, or magnets.
 8. Method according to claim 3, furthercomprising sucking the transducer element onto the tool by means of atleast one vacuum duct in the tool body.
 9. Method according to claim 8,wherein a pressure compensation takes place on radially outer areas ofthe sucked on transducer element by means of compensating ducts in thetool body.
 10. Method according to claim 1, further comprising removingthe transducer centring device prior to fixing the transducer element inthe bush.
 11. Method according to claim 1, wherein the fixing of thetransducer element in the bush is provided by at least partly fillinggaps with at least one of: foam or moulding material.
 12. Methodaccording to claim 1, wherein use is made of a tool with steps, which asa stop engages with at least one of: a front end or a setback shoulderof the bush.
 13. Method according to claim 1, further comprisingmanufacturing several transducer units in parallel using a plurality oftransducer receptacles and bush receptacles.
 14. Method according toclaim 1, further comprising fixing the bush relative to the tool. 15.Method according to claim 14, wherein the fixing of the bush is providedusing a holder provided on the tool.
 16. Method according to claim 1,further comprising inserting and fixing several transducer elements inthe angled bush.
 17. Method according to claim 1, further comprisingpressing a shielding can into the bush.
 18. Method according to claim17, further comprising fixing the shielding can to a printed circuitboard.
 19. Method according to claim 18, further comprising solderingthe shielding can to the printed circuit board.
 20. Method according toclaim 17, further comprising soldering the transducer unit to theshielding can.
 21. Method according to claim 18, further comprisingsoldering the transducer unit to the shielding can.
 22. Method accordingto claim 20, further comprising soldering the transducer unit to theshielding can by means of at least one clip provided thereon.
 23. Methodaccording to claim 1, further comprising bringing the bush into at leastone of: a positive, a non-positive engagement, or a locking engagementwith a printed circuit board.